Of the ones you mention and if all were the same price my pick would be the Heym! However they are not all the same price and because of that fact my #1 pick would be the Merkel, #2 Krieghoff, and #3 would be the Chapuis! I now own two Merkel double rifles, one a 140-2 Safari 470NE, and a 140E-1, 9.3X74R Both are around ten years old, and have been shot quite a lot and both are as new! The 9.3X74R has taken most of the north American game short of the large brown bear and mountain sheep. The 470NE has taken two bull Elephant, and three cape Buffalo bulls, not by me but the previous owner, With me it has only take several large Russian boar! So since these two double rifles are the only Merkel double rifles I've owned, I have owed several Merkel shotguns, and combination guns over the years and have never had a major problem with any of them.

I have also owned one Heym double rifle chambered for 450NE 3 1/4 in and it took three buffalo and a lot of North American and African plains game. That rifle was an old mod 88 with selective ejector/extractor switch, a feature I really liked!

I have not owned a Chapuis double rifle but have several friends who own and shoot Chapuis doubles and I have never seen one that was not accurate. Some things about the Chapuis I do not like, things like the beavertail fore stock, and they tend to be too light for chambering IMO.

The Krieghoff doubles do not fit me well and that is the only reason I do not own one. I have zero issue with the K-gun's de-cocking system. With this rifle loaded, and de-cocked it is the safest double rifle on the market today to avoid an accidental discharge. The rifle once cocked, fired, and broken open for a re-loading of one or both chambers the rifle has re-cocked it's self and can be fired the instant it is closed. If the rifle is not fired again after the reload, all that is needed to make it safe is to push the de-cocking liver (so-called safety) forward slightly and released, the rifle is then un-cocked and safe to carry loaded.

NOW we come to the Blaser S2 double rifle that everyone thinks the de-cocking system is the same as the Krieghoff, but there is one seriously negative feature in the S2 that , IMO, makes it not the best choice for use as a dangerous game rifle.

This rifle automatically DE-COCKS it's self, if opened for ANY REASON! With two shots in a Buffalo that is still on his feet and coming fast this rifle must be RE-COCKED before it can be fired! IMO, that is not a feature I want on a double rifle I'm facing a mauling with. When every maker of hammerless dangerous game double rifles in the world frowns on a simple auto safety on their rifles used for dangerous game, not one of them would even consider a system the automatically DE-COCKED the rifle when it was opened for a re-load! With this in mind I certainly cannot recommend the Blaser S-2 if the rifle will be used for dangerous game! I certainly would not buy one!

Hope any of this helps in your choice, and that choice is, in the final analyses, your’s